1. Technical Field
The invention relates to an audio system for modifying an input surround sound signal and for generating a spatially equilibrated output surround sound signal.
2. Related Art
The human perception of loudness is a phenomenon that has been investigated and better understood in recent years. One phenomenon of human perception of loudness is a nonlinear and frequency varying behavior of the auditory system.
Furthermore, surround sound sources are known in which dedicated audio signal channels are generated for the different loudspeakers of a surround sound system. Due to the nonlinear and frequency varying behavior of the human auditory system, a surround sound signal having a first sound pressure may be perceived as spatially balanced meaning that a user has the impression that the same signal level is being received from all different directions. When the same surround sound signal is output at a lower sound pressure level, it is often detected by the listening user as a change in the perceived spatial balance of the surround sound signal. By way of example, it can be detected by the listening user that at lower signal levels the side or the rear surround sound channels are perceived with less loudness compared to a situation with higher signal levels. As a consequence, the user has the impression that the spatial balance is lost and that the sound “moves” to the front loudspeakers.